<!--
  例子:

  请输入后 - 点击 切换类型
 -->

 <!DOCTYPE html>
 <html lang="en">
 <head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Document</title>
 </head>
 <body>
   <div id="app">
     <span v-if="isUser">
       <label for="username">用户账号</label>
       <input type="text" id='username' placeholder="用户账户">
     </span>

     <span v-else>
       <label for="email">用户邮箱</label>
       <input type="text" id='email' placeholder="用户邮箱">
     </span>

     <button @click='isUser = !isUser'>切换类型</button>
   </div>

   <script src='/vue.js'></script>
   <script>
     new Vue({
       el: '#app',
       data: {
         isUser: true
       }
     })
   </script>
 </body>
 </html>